Fluid Dynamics

Char conversion for oxyfuel in CFD calculations

The heterogeneous combustion of solid fuel particles is a complex process. Under oxyfuel conditions for CCS, where fuel is burned in the presence of high concentrations of carbon dioxide and water vapour, this process is more difficult to model due to these gas species competing to react with the carbon surface. Traditionally, simplified models have been used in CFD calculations to approximate this combustion behaviour, however with more powerful computing resources available, it is now possible to significantly increase the fidelity of models describing reactive particles. Research work is required to develop and validate these high fidelity methods for practical combustion systems of conventional and oxyfuel fired conditions, to evaluate the impact of these treatments, potentially improving the modelling capability for solid fuel combustion, which will help drive improvements to the efficiency and performance of such systems, providing improvements for future clean combustion systems.

Particle motion and combustion in turbulent flows

The simulation of solid fuel combustion systems relies on the resolution of particle trajectories within the fluid domain. The widely used RANS approach to solving the fluid properties of a turbulent flow only resolves time-averaged quantities, which are not representative of the forces applied to the particle trajectories. Modelling investigations are required to improve methods that apply turbulent fluctuations in the velocity field to the particle motion, as well as methods to resolve gas species concentrations on the heterogeneous reactions of combusting particles, and can be applied to CFD calculations of combustion facilities.

Radiative transfer for biomass particles

The combustion of biomass for energy production is attracting a growing interest academically and industrially as a means to reduce the sector’s impact on climate forcing. Modelling will play a key role in the design of optimal biomass combustion systems, however there is a need to adapt currently adopted models for solid fuel combustion to take into account the unique challenges that biomass combustion introduces. Among these is the irregular shapes of biomass particles, which tend to depart significantly from the ideally spherical assumption that is widely adopted. Studies into investigating the impact of these shape irregularities on radiative transfer to the particle, the dominant mode of heat transfer at combustion temperatures, to better represent the ignition and combustion of biomass.

Turbulence modelling of combustion using Large Eddie Simulations (LES)

Computational Fluid Dynamics modelling is a powerful tool that, due to recent advances in computational power, has become useful in aiding the design and development of advanced power generation technologies with significant climate change mitigation potential. Large Eddie Simulations (LES) is an advanced turbulence modelling approach with the potential to more accurately predict the combustion phenomena that drive the heat transfer, pollutant emissions, and fuel burnout of coal, gas and biomass fired power plants. However, development work based on experimental validation is necessary to make the technique more reliable and commercially applicable to the power generation sector.

The project will characterise the near burner velocity field of a 250 kW test furnace at the Pilot Scale Advanced Capture Technology (PACT) Facilities using a velocity measurement probe. This experimental data will be used to develop and validate advanced LES modelling approaches as part of a large CFD group focused on energy research.

The aim will be to improve the existing LES turbulence modelling methods and drive forward the commercialisation of the approach to the power generation sector.

Particle motion in turbulent flows

The simulation of two-phase dispersed systems often rely on the resolution of particle trajectories within the fluid domain. The widely used RANS approach to solving the fluid properties of a turbulent flow only resolves time-averaged quantities, which are not representative of the forces applied to the particle trajectories. Modelling investigations are required to improve methods that apply turbulent fluctuations in the velocity field to the particle motion, as well as methods to resolve gas species concentrations on the heterogeneous reactions that may occur, with these approaches being applicable to CFD calculations of practical facilities.